Extraction, Characterization, Interpretation of Natural Dyes with its Application and Degradation Studies

Natural dye refers to a colouring substance obtained from natural sources, especially plants, which is used in the study and evaluation of crude drugs.These dyes occur in various plant parts such as roots, leaves, bark, and flowers, and contain phytochemicals like flavonoids, tannins, curcumin, and anthocyanins. They are useful for identification purposes and may also be used in herbal formulations ^1-5.

Natural dyes are preferred because they are non-toxic, biodegradable, and compatible with herbal drugs, making them safer than synthetic colouring agents.

Natural dyes are generally known as colorants and mostly founds from different plants parts like root (turmeric, beet), leaves (indigo, tea), bark (alder), fruits/seed (pomegranate, berries, coriander), flowers (marigold). Different types of insects like cochineal or lac produce natural dye vibrant red while minerals like ochre also provide earth tones ^6-11.

Importance of Natural Dyes:

Natural dyes are important in the pharmaceutical field due to their safety, low toxicity, and biodegradable nature. They are used as indicators to monitor pH changes during drug formulation and quality testing.

These dyes are also applied as colouring agents in medicines, improving appearance and patient acceptance. Being naturally derived, they reduce the risk of harmful side effects compared to synthetic dyes.

In addition, natural dyes are cost-effective and easily available, making them useful in basic testing and in areas with limited resources. However, their use is limited in advanced applications due to lower stability and precision ¹¹.

ADVANTAGES& DISADVANTAGES:

Table-1: Advantages and Disadvantages of Natural dyes ^{12, 13}

Natural dyes are collected from different plants parts. Natural dyes are biodegradable, harmless and friendly with environment in contrast with synthetic dyes. In this research we collect dyes from different plant sources like Thea sinensis (Tea), Curcuma longa (Turmeric), Beta vulgaris (Beet Root), Coriandrum sativum (Coriander) ¹¹.

Table-2:  Introduction about selected plant

Name of Plant	Biological Source	Geographical source	Plant parts used	Picture
Tea 14	Thea sinensis Family-Theaceae	China, India, Kenya, and Sri Lanka	Leaves
Turmeric 15	Curcuma longa Family-Zingiberaceae	India, Vietnam, China, Myanmar	Rhizomes
Beetroot 16	Beta vulgaris Family-Amaranthaceae	Russia, France, United state, Germany	Roots
Coriander 17	Coriandrum sativum Family-Apiaceae	India, Morocco, Canada, Russia, Romania	Leaf

Four plant sources were selected for extraction of natural dyes based on their colour properties. Tea and coriander were selected for brown and green shades respectively, while turmeric and beetroot were chosen for yellow and red colours. Fresh plant materials were collected from local sources and cleaned thoroughly with tap water before use.

Table-3: Chemical constituents and extract colour of selected plant

Sr. No	Plant name	Chemical Constituents	Colour	Pictures
1.	Tea 14	Catechins, flavanols, Caffeine, theobromine, theophylline.	Brown
2.	Turmeric 15	α-phellandrene, zingiberene, sabinene, cineol, and sesquiterpenoids, Curcumin	Yellow
3.	Beetroot 16	Betacyanin and Betaxanthins, Phenolic acids and flavonoids.	Red
4.	Coriander 17	Linalool, pinene, -terpinene, camphor, and geraniol, Polyphenols, Flavonoids	Green

MATERIAL AND METHODS:

Chemicals, Instruments and Equipment

Chemicals:

Distilled water, sodium hydroxide, copper sulphate, Sulphuric acid, Ferrous Sulphate, Chloroform, Boric Acid, Molisch reagent

Instruments:

Analytical balance was used for accurate weighing of plant materials. A centrifuge and filtration setup were used for separation of extracts.  IR spectrophotometer was used for characterization studies.

Equipment:

Laboratory equipment such as beakers, conical flasks, test tubes, measuring cylinders, mortar and pestle, blender, pipettes, petri dishes, and glass rods were used. Water bath was used for extraction, and filter paper was used for filtration.

Collection of Plant Materials

Plant materials such as tea, turmeric, beetroot and coriander were selected based on their natural colouring properties. The samples were collected from local markets and nearby areas. All materials were properly identified and cleaned to remove dust and impurities.

Drying of Plant Materials

They were then cut into small pieces and dried under shade at room temperature to preserve their chemical constituents. Direct sunlight was avoided to prevent degradation of active compounds. The drying process was continued until the materials became completely moisture-free, after which they were stored in clean, dry containers for further use.

Extraction of Natural Dyes:

Collect 50 gm plant materials by using a digital balance. The chopped plant materials were dipped in 200 ml of distilled water in a beaker and heated at a temperature range of 35-40°C until the dye was released. The dye from aqueous extraction was filtered through sieve, then container of hot extractive was kept in cold water.

Figure no-1: Extraction of different Plants

RESULT AND DISCUSSION

The extracted dyes showed a good colour-imparting ability and were of the desirable consistency.

Screening of those extracted components:                                         

Different Chemical Test of Extract:

Table-4: Different Chemical Test of Extract

Characterization of Dyes: Using FT-IR Spectrum

Fourier Transform Infrared Spectroscopy (FT-IR) is an important analytical technique used for the characterization of dyes. It helps in identifying the different functional groups present in the dye molecules by measuring the absorption of infrared radiation at various wavelengths. This method is widely used for both natural and synthetic dyes to understand their chemical structure and confirm the presence of specific bonding groups. FT-IR is commonly used in dye research to detect groups such as hydroxyl, carbonyl, amino, and aromatic compounds.

In FT-IR analysis, a small amount of the extracted dye sample is placed in the instrument, and infrared light is passed through it. Different chemical bonds absorb IR radiation at characteristic frequencies, producing a spectrum in the range of 4000–400 cm?¹. The obtained spectrum acts like a fingerprint of the dye compound, which helps in determining its molecular composition.

Figure no-2: IR Spectrum (Tea)

Figure no-3: IR Spectrum (Turmeric)

Figure no-4: IR Spectrum (Beetroot)

Figure no 5: IR Spectrum (Coriander)

Application of Dyes to Fabrics:

The dye is applied to fabric by two methods

• Without Mordant
• With mordant

Mordant:

• Copper Sulphate (CuSO₄): 0.05 g of Copper Sulphate was dissolved in 50 mL of distilled water.
• Ferrous Sulphate (FeSO₄): 0.05 g of Ferrous Sulphate was dissolved in 50 mL of distilled water.

       Figure-6: Extract plant with CuSO₄                      Figure-7: Extract plant with FeSO₄

Comparison of colour in paper with and without mordant:

Table-5: Comparison of colour in paper with and without mordant

Application of dyes in cotton:        

The stability, colour, and functionalitycontaining natural dyes were greatly impacted by the storage temperature. It was discovered that the manufactured remained stable for up to four weeks when stored at room temperature and 4 ° C. They added an intense colour and had a decent consistency. Additionally, because the dyes were made with only natural chemicals, they left the skin feeling calm and refreshed. The stability and shelf life of natural dyes depends on several factors, including the type of dye, exposure to environmental elements.

Figure - 8: Using different plant dyes in filter paper without, CuSO4, FeSO4 mordants

Table-6: Application of selected natural plants

Degradation rates factor of selected natural dyes:

Natural dyes obtained from plants gradually lose their colour strength due to different environmental and chemical factors. This process is called degradation. The stability of the dye depends on the nature of the pigment present in each plant source.

Table-7: Degradation rates factor of selected natural dyes